Package scala.collection.mutable

This class implements mutable maps with AnyRef keys based on a hash table with open addressing.

Basic map operations on single entries, including contains and get, are typically significantly faster with AnyRefMap than HashMap. Note that numbers and characters are not handled specially in AnyRefMap; only plain equals and hashCode are used in comparisons.

Methods that traverse or regenerate the map, including foreach and map, are not in general faster than with HashMap. The methods foreachKey, foreachValue, mapValuesNow, and transformValues are, however, faster than alternative ways to achieve the same functionality.

Maps with open addressing may become less efficient at lookup after repeated addition/removal of elements. Although AnyRefMap makes a decent attempt to remain efficient regardless, calling repack on a map that will no longer have elements removed but will be used heavily may save both time and storage space.

This map is not intended to contain more than 2²⁹ entries (approximately 500 million). The maximum capacity is 2³⁰, but performance will degrade rapidly as 2³⁰ is approached.

An implementation of the Buffer class using an array to represent the assembled sequence internally. Append, update and random access take constant time (amortized time). Prepends and removes are linear in the buffer size.

A builder class for arrays.

A common supertrait of ArrayOps and WrappedArray that factors out the deep method for arrays and wrapped arrays and serves as a marker trait for array wrappers.

This class serves as a wrapper for Arrays with all the operations found in indexed sequences. Where needed, instances of arrays are implicitly converted into this class.

The difference between this class and WrappedArray is that calling transformer methods such as filter and map will yield an array, whereas a WrappedArray will remain a WrappedArray.

A class for polymorphic arrays of elements that's represented internally by an array of objects. This means that elements of primitive types are boxed.

Simple stack class backed by an array. Should be significantly faster than the standard mutable stack.

A class for mutable bitsets.

Bitsets are sets of non-negative integers which are represented as variable-size arrays of bits packed into 64-bit words. The memory footprint of a bitset is determined by the largest number stored in it.

Buffers are used to create sequences of elements incrementally by appending, prepending, or inserting new elements. It is also possible to access and modify elements in a random access fashion via the index of the element in the current sequence.

A template trait for buffers of type Buffer[A].

Buffers are used to create sequences of elements incrementally by appending, prepending, or inserting new elements. It is also possible to access and modify elements in a random access fashion via the index of the element in the current sequence.

The base trait of all builders. A builder lets one construct a collection incrementally, by adding elements to the builder with += and then converting to the required collection type with result.

One cannot assume that a single Builder can build more than one instance of the desired collection. Particular subclasses may allow such behavior. Otherwise, result should be treated as a terminal operation: after it is called, no further methods should be called on the builder. Extend the collection.mutable.ReusableBuilder trait instead of Builder for builders that may be reused to build multiple instances.

A trait for cloneable collections.

Class used internally for default map model.

An implementation class backing a HashSet.

This trait is used internally. It can be mixed in with various collections relying on hash table as an implementation.

The canonical builder for collections that are growable, i.e. that support an efficient += method which adds an element to the collection.

GrowableBuilders can produce only a single instance of the collection they are growing.

Class used internally.

This class implements mutable maps using a hashtable.

This class implements mutable sets using a hashtable.

This class can be used to construct data structures that are based on hashtables. Class HashTable[A] implements a hashtable that maps keys of type A to values of the fully abstract member type Entry. Classes that make use of HashTable have to provide an implementation for Entry.

There are mainly two parameters that affect the performance of a hashtable: the initial size and the load factor. The size refers to the number of buckets in the hashtable, and the load factor is a measure of how full the hashtable is allowed to get before its size is automatically doubled. Both parameters may be changed by overriding the corresponding values in class HashTable.

History[A, B] objects may subscribe to events of type A published by an object of type B. The history subscriber object records all published events up to maximum number of maxHistory events.

A subtrait of scala.collection.IndexedSeq which represents sequences that can be mutated.

It declares a method update which allows updating an element at a specific index in the sequence.

This trait just implements iterator in terms of apply and length. However, see IndexedSeqOptimized for an implementation trait that overrides operations to make them run faster under the assumption of fast random access with apply.

A subtrait of scala.collection.IndexedSeq which represents sequences that can be mutated.

A non-strict view of a mutable IndexedSeq.

A view is a lazy version of some collection. Collection transformers such as map or filter or ++ do not traverse any elements when applied on a view. Instead they create a new view which simply records that fact that the operation needs to be applied. The collection elements are accessed, and the view operations are applied, when a non-view result is needed, or when the force method is called on a view. Some of the operations of this class will yield again a mutable indexed sequence, others will just yield a plain indexed sequence of type collection.IndexedSeq. Because this is a leaf class there is no associated Like class.

A base trait for iterable collections that can be mutated.

This is a base trait for all mutable Scala collections that define an iterator method to step through one-by-one the collection's elements. Implementations of this trait need to provide a concrete method with signature:

def iterator: Iterator[A]

They also need to provide a method newBuilder which creates a builder for collections of the same kind.

This trait implements Iterable's foreach method by stepping through all elements using iterator. Subclasses should re-implement foreach with something more efficient, if possible.

This trait adds methods iterator, sameElements, takeRight, dropRight to the methods inherited from trait `Traversable`.

Note: This trait replaces every method that uses break in TraversableLike by an iterator version.

A builder that constructs its result lazily. Iterators or iterables to be added to this builder with ++= are not evaluated until result is called.

This builder can be reused.

A subtrait of collection.LinearSeq which represents sequences that can be mutated.

Linear sequences have reasonably efficient head, tail, and isEmpty methods. If these methods provide the fastest way to traverse the collection, a collection Coll that extends this trait should also extend LinearSeqOptimized[A, Coll[A]].

Class for the linked hash map entry, used internally.

This class implements mutable maps using a hashtable. The iterator and all traversal methods of this class visit elements in the order they were inserted.

This class implements mutable sets using a hashtable. The iterator and all traversal methods of this class visit elements in the order they were inserted.

A Buffer implementation backed by a list. It provides constant time prepend and append. Most other operations are linear.

A simple mutable map backed by a list, so it preserves insertion order.

This class implements mutable maps with Long keys based on a hash table with open addressing.

Basic map operations on single entries, including contains and get, are typically substantially faster with LongMap than HashMap. Methods that act on the whole map, including foreach and map are not in general expected to be faster than with a generic map, save for those that take particular advantage of the internal structure of the map: foreachKey, foreachValue, mapValuesNow, and transformValues.

Maps with open addressing may become less efficient at lookup after repeated addition/removal of elements. Although LongMap makes a decent attempt to remain efficient regardless, calling repack on a map that will no longer have elements removed but will be used heavily may save both time and storage space.

This map is not intended to contain more than 2^{29 entries (approximately 500 million). The maximum capacity is 2}30, but performance will degrade rapidly as 2^30 is approached.

A base trait for maps that can be mutated.

Implementation note: This trait provides most of the operations of a mutable Map independently of its representation. It is typically inherited by concrete implementations of maps.

To implement a concrete mutable map, you need to provide implementations of the following methods:

def get(key: K): Option[V]
def iterator: Iterator[(K, V)]
def += (kv: (K, V)): This
def -= (key: K): This

If you wish that methods like take, drop, filter also return the same kind of map you should also override:

def empty: This

It is also good idea to override methods foreach and size for efficiency.

The canonical builder for immutable maps, working with the map's + method to add new elements. Collections are built from their empty element using this + method.

A template trait for mutable maps.

Implementation note: This trait provides most of the operations of a mutable Map independently of its representation. It is typically inherited by concrete implementations of maps.

To implement a concrete mutable map, you need to provide implementations of the following methods:

def get(key: K): Option[V]
def iterator: Iterator[(K, V)]
def += (kv: (K, V)): This
def -= (key: K): This

If you wish that methods like take, drop, filter also return the same kind of map you should also override:

def empty: This

It is also good idea to override methods foreach and size for efficiency.

A trait for mutable maps with multiple values assigned to a key.

This class is typically used as a mixin. It turns maps which map A to Set[B] objects into multimaps that map A to B objects.

This class is used internally to represent mutable lists. It is the basis for the implementation of the class Queue.

A mutable hash map based on an open hashing scheme. The precise scheme is undefined, but it should make a reasonable effort to ensure that an insert with consecutive hash codes is not unnecessarily penalised. In particular, mappings of consecutive integer keys should work without significant performance loss.

This class implements priority queues using a heap. To prioritize elements of type A there must be an implicit Ordering[A] available at creation.

If multiple elements have the same priority in the ordering of this PriorityQueue, no guarantees are made regarding the order in which elements are returned by dequeue or dequeueAll. In particular, that means this class does not guarantee first in first out behaviour that may be incorrectly inferred from the Queue part of the name of this class.

Only the dequeue and dequeueAll methods will return elements in priority order (while removing elements from the heap). Standard collection methods including drop, iterator, and toString will remove or traverse the heap in whichever order seems most convenient.

Therefore, printing a PriorityQueue will not reveal the priority order of the elements, though the highest-priority element will be printed first. To print the elements in order, one must duplicate the PriorityQueue (by using clone, for instance) and then dequeue them:

Publisher[A,This] objects publish events of type A to all registered subscribers. When subscribing, a subscriber may specify a filter which can be used to constrain the number of events sent to the subscriber. Subscribers may suspend their subscription, or reactivate a suspended subscription. Class Publisher is typically used as a mixin. The abstract type Pub models the type of the publisher itself.

Queue objects implement data structures that allow to insert and retrieve elements in a first-in-first-out (FIFO) manner.

This class is used internally to implement data structures that are based on resizable arrays.

ReusableBuilder is a marker trait that indicates that a Builder can be reused to build more than one instance of a collection. In particular, calling result followed by clear will produce a collection and reset the builder to begin building a new collection of the same type.

It is up to subclasses to implement this behavior, and to document any other behavior that varies from standard ReusableBuilder usage (e.g. operations being well-defined after a call to result, or allowing multiple calls to result to obtain different snapshots of a collection under construction).

A revertible history is a History object which supports an undo operation. Type variable Evt refers to the type of the published events, Pub denotes the publisher type. Type Pub is typically a subtype of Publisher.

A subtrait of collection.Seq which represents sequences that can be mutated.

Sequences are special cases of iterable collections of class Iterable. Unlike iterables, sequences always have a defined order of elements. Sequences provide a method apply for indexing. Indices range from 0 up to the length of a sequence. Sequences support a number of methods to find occurrences of elements or subsequences, including segmentLength, prefixLength, indexWhere, indexOf, lastIndexWhere, lastIndexOf, startsWith, endsWith, indexOfSlice.

Another way to see a sequence is as a PartialFunction from Int values to the element type of the sequence. The isDefinedAt method of a sequence returns true for the interval from 0 until length.

Sequences can be accessed in reverse order of their elements, using methods reverse and reverseIterator.

Sequences have two principal subtraits, IndexedSeq and LinearSeq, which give different guarantees for performance. An IndexedSeq provides fast random-access of elements and a fast length operation. A LinearSeq provides fast access only to the first element via head, but also has a fast tail operation.

The class adds an update method to collection.Seq.

A template trait for mutable sequences of type mutable.Seq[A].

A generic trait for mutable sets.

To implement a concrete mutable set, you need to provide implementations of the following methods:

def contains(elem: A): Boolean
def iterator: Iterator[A]
def += (elem: A): this.type
def -= (elem: A): this.type

If you wish that methods like take, drop, filter return the same kind of set, you should also override:

def empty: This

It is also good idea to override methods foreach and size for efficiency.

The canonical builder for mutable Sets.

A template trait for mutable sets of type mutable.Set[A].

This trait provides most of the operations of a mutable.Set independently of its representation. It is typically inherited by concrete implementations of sets.

To implement a concrete mutable set, you need to provide implementations of the following methods:

def contains(elem: A): Boolean
def iterator: Iterator[A]
def += (elem: A): this.type
def -= (elem: A): this.type

If you wish that methods like take, drop, filter return the same kind of set, you should also override:

def empty: This

It is also good idea to override methods foreach and size for efficiency.

A mutable map whose keys are sorted.

A builder for mutable sequence of characters. This class provides an API mostly compatible with java.lang.StringBuilder, except where there are conflicts with the Scala collections API (such as the reverse method.)

Subscriber[A, B] objects may subscribe to events of type A published by an object of type B. B is typically a subtype of scala.collection.mutable.Publisher.

A trait for traversable collections that can be mutated.

This is a base trait of all kinds of mutable Scala collections. It implements the behavior common to all collections, in terms of a method foreach with signature:

def foreach[U](f: Elem => U): Unit

Collection classes mixing in this trait provide a concrete foreach method which traverses all the elements contained in the collection, applying a given function to each. They also need to provide a method newBuilder which creates a builder for collections of the same kind.

A traversable class might or might not have two properties: strictness and orderedness. Neither is represented as a type.

The instances of a strict collection class have all their elements computed before they can be used as values. By contrast, instances of a non-strict collection class may defer computation of some of their elements until after the instance is available as a value. A typical example of a non-strict collection class is a scala.collection.immutable.Stream. A more general class of examples are TraversableViews.

If a collection is an instance of an ordered collection class, traversing its elements with foreach will always visit elements in the same order, even for different runs of the program. If the class is not ordered, foreach can visit elements in different orders for different runs (but it will keep the same order in the same run).'

A typical example of a collection class which is not ordered is a HashMap of objects. The traversal order for hash maps will depend on the hash codes of its elements, and these hash codes might differ from one run to the next. By contrast, a LinkedHashMap is ordered because its foreach method visits elements in the order they were inserted into the HashMap.

A mutable sorted map implemented using a mutable red-black tree as underlying data structure.

A mutable sorted set implemented using a mutable red-black tree as underlying data structure.

Classes that mix in the Undoable class provide an operation undo which can be used to undo the last operation.

A buffer that stores elements in an unrolled linked list.

Unrolled linked lists store elements in linked fixed size arrays.

Unrolled buffers retain locality and low memory overhead properties of array buffers, but offer much more efficient element addition, since they never reallocate and copy the internal array.

However, they provide O(n/m) complexity random access, where n is the number of elements, and m the size of internal array chunks.

Ideal to use when:

elements are added to the buffer and then all of the elements are traversed sequentiallytwo unrolled buffers need to be concatenated (see concat)

Better than singly linked lists for random access, but should still be avoided for such a purpose.

A hash map with references to entries which are weakly reachable. Entries are removed from this map when the key is no longer (strongly) referenced. This class wraps java.util.WeakHashMap.

A class representing Array[T].

A builder class for arrays.

This builder can be reused.

This is a simple proxy class for `scala.collection.mutable.Buffer`. It is most useful for assembling customized set abstractions dynamically using object composition and forwarding.

This class is used internally. It implements the mutable Map class in terms of three functions: findEntry, addEntry, and entries.

This class implements double linked lists where both the head (elem), the tail (next) and a reference to the previous node (prev) are mutable.

This extensible class may be used as a basis for implementing double linked lists. Type variable A refers to the element type of the list, type variable This is used to model self types of linked lists.

The invariant of this data structure is that prev is always a reference to the previous node in the list. If this is the first node of the list, prev will be null. Field next is set to this iff the list is empty.

Examples (right arrow represents next, left arrow represents prev, _ represents no value):

Empty:

null <-- [ _ ] --,
         [   ] <-`

Single element:

null <-- [ x ] --> [ _ ] --,
         [   ] <-- [   ] <-`

More elements:

null <-- [ x ] --> [ y ] --> [ z ] --> [ _ ] --,
         [   ] <-- [   ] <-- [   ] <-- [   ] <-`

This class can be used as an adaptor to create mutable maps from immutable map implementations. Only method empty has to be redefined if the immutable map on which this mutable map is originally based is not empty. empty is supposed to return the representation of an empty map.

This class can be used as an adaptor to create mutable sets from immutable set implementations. Only method empty has to be redefined if the immutable set on which this mutable set is originally based is not empty. empty is supposed to return the representation of an empty set.

A more traditional/primitive style of linked list where the "list" is also the "head" link. Links can be manually created and manipulated, though the use of the API, when possible, is recommended.

The danger of directly manipulating next:

scala> val b = LinkedList(1)
b: scala.collection.mutable.LinkedList[Int] = LinkedList(1)

scala> b.next = null

scala> println(b)
java.lang.NullPointerException

If the list is empty next must be set to this. The last node in every mutable linked list is empty.

Examples (_ represents no value):

Empty:

[ _ ] --,
[   ] <-`

Single element:

[ x ] --> [ _ ] --,
          [   ] <-`

More elements:

[ x ] --> [ y ] --> [ z ] --> [ _ ] --,
                              [   ] <-`

This extensible class may be used as a basis for implementing linked list. Type variable A refers to the element type of the list, type variable This is used to model self types of linked lists.

If the list is empty next must be set to this. The last node in every mutable linked list is empty.

Examples (_ represents no value):

Empty:

[ _ ] --,
[   ] <-`

Single element:

[ x ] --> [ _ ] --,
          [   ] <-`

More elements:

[ x ] --> [ y ] --> [ z ] --> [ _ ] --,
                              [   ] <-`

This trait implements a proxy for scala.collection.mutable.Map.

It is most useful for assembling customized map abstractions dynamically using object composition and forwarding.

This class is typically used as a mixin. It adds a subscription mechanism to the Buffer class into which this abstract class is mixed in. Class ObservableBuffer publishes events of the type Message.

This class is typically used as a mixin. It adds a subscription mechanism to the Map class into which this abstract class is mixed in. Class ObservableMap publishes events of the type Message.

This class is typically used as a mixin. It adds a subscription mechanism to the Set class into which this abstract class is mixed in. Class ObservableSet publishes events of the type Message.

This class servers as a proxy for priority queues. The elements of the queue have to be ordered in terms of the Ordered[T] class.

Queue objects implement data structures that allow to insert and retrieve elements in a first-in-first-out (FIFO) manner.

This is a simple wrapper class for scala.collection.mutable.Set. It is most useful for assembling customized set abstractions dynamically using object composition and forwarding.

A stack implements a data structure which allows to store and retrieve objects in a last-in-first-out (LIFO) fashion.

A stack implements a data structure which allows to store and retrieve objects in a last-in-first-out (LIFO) fashion.

This class should be used as a mixin. It synchronizes the Buffer methods of the class into which it is mixed in.

This class should be used as a mixin. It synchronizes the Map functions of the class into which it is mixed in.

This class implements synchronized priority queues using a binary heap. The elements of the queue have to be ordered in terms of the Ordered[T] class.

This is a synchronized version of the Queue[T] class. It implements a data structure that allows one to insert and retrieve elements in a first-in-first-out (FIFO) manner.

This class should be used as a mixin. It synchronizes the Set functions of the class into which it is mixed in.

This is a synchronized version of the Stack[T] class. It implements a data structure which allows to store and retrieve objects in a last-in-first-out (LIFO) fashion.